Re: [PATCH 1/2] drm/i915/guc: Advance over port[0] if set and not preempting

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> Our execlist emulation is intended to only use a maximum of 2 ports per
> engine, so as to not overflow the wq. (By knowing the limits, we can
> avoid having to handle the wq exhaustion.) However, upon adding
> preemption, we lost the skip over the first port if set for the
> non-preemption path. Restore it.
>
> Reported-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> Fixes: c41937fd994a ("drm/i915/guc: Preemption! With GuC")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Michał Winiarski <michal.winiarski@intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>

Now it makes sense to me. You might want a stamp from Michał too.

Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

> ---
>  drivers/gpu/drm/i915/intel_guc_submission.c | 29 ++++++++++++++++-------------
>  1 file changed, 16 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_guc_submission.c b/drivers/gpu/drm/i915/intel_guc_submission.c
> index cbf5a96f5806..70e64bdb73dd 100644
> --- a/drivers/gpu/drm/i915/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/intel_guc_submission.c
> @@ -743,23 +743,26 @@ static void guc_dequeue(struct intel_engine_cs *engine)
>  	if (!rb)
>  		goto unlock;
>  
> -	if (HAS_LOGICAL_RING_PREEMPTION(engine->i915) && port_isset(port)) {
> -		struct guc_preempt_work *preempt_work =
> -			&engine->i915->guc.preempt_work[engine->id];
> -
> -		if (rb_entry(rb, struct i915_priolist, node)->priority >
> -		    max(port_request(port)->priotree.priority, 0)) {
> -			execlists_set_active(execlists,
> -					     EXECLISTS_ACTIVE_PREEMPT);
> -			queue_work(engine->i915->guc.preempt_wq,
> -				   &preempt_work->work);
> -			goto unlock;
> -		} else if (port_isset(last_port)) {
> -			goto unlock;
> +	if (port_isset(port)) {
> +		if (HAS_LOGICAL_RING_PREEMPTION(engine->i915)) {
> +			struct guc_preempt_work *preempt_work =
> +				&engine->i915->guc.preempt_work[engine->id];
> +
> +			if (rb_entry(rb, struct i915_priolist, node)->priority >
> +			    max(port_request(port)->priotree.priority, 0)) {
> +				execlists_set_active(execlists,
> +						     EXECLISTS_ACTIVE_PREEMPT);
> +				queue_work(engine->i915->guc.preempt_wq,
> +					   &preempt_work->work);
> +				goto unlock;
> +			}
>  		}
>  
>  		port++;
> +		if (port_isset(port))
> +			goto unlock;
>  	}
> +	GEM_BUG_ON(port_isset(port));
>  
>  	do {
>  		struct i915_priolist *p = rb_entry(rb, typeof(*p), node);
> -- 
> 2.15.0
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